1. Field of the Invention
The disclosures discussed herein relate to an image display apparatus and an image display system.
2. Description of the Related Art
Energy saving has been required for office and home apparatuses along with recent increases in electricity rates due to rises in resources and energy prices.
In the related art image projection apparatuses, there is known in the art a technology to shift an electric energy mode to an energy-saving mode to restrict use of functions of the image projection apparatuses when a no-signal state without user's operations continues for a certain period of time to reduce electric energy consumption (e.g., Patent Document 1).
Although there is known in the related art the above technology to shift the electric energy mode to the energy-saving mode due to the no-signal state for a certain period of time, a period of the no-signal state of the image projection apparatus may vary with scenes in which users use the corresponding image projection apparatus. For example, when a user inputs data into the image projection apparatus via a USB cable, the user simply inserts the USB cable to input data, and hence the no-signal state of the image projection apparatus in this case may be shorter than that of the image projection apparatus in which data are input via a network. On the other hand, when data are input into the image projection apparatus via a network, settings are required in a terminal side network to which the image projection apparatus is connected. Hence, the no-signal state in this case is longer than that of the image projection apparatus in which data are input via the USB cable.
However, in the related art technology to shift the image projection apparatus to the energy-saving mode, time required for shifting from a normal-energy mode to the energy-saving mode is a predetermined time. Hence, electric power may be wasted due to elongated time required for shifting from the normal-energy mode to the energy mode, or the image projection apparatus may shift to the energy mode before the image projection apparatus is used due to insufficient time. Note that the above disadvantageous effects may also be observed in image display apparatuses.